Pawl and ratchet stepping mechanisms



M. HUBER ET AL PAWL AND RA'I'CHET STEPPING MECHANISMS June 24, 1969 Sheet of 4 Q Filed July 10, 1967 June 24,1969 Y M. HUBER ETAL 3,451,279

PAWL AND mwcnm: STEPPING MECHANISMS Filed July 10. 1967 Sheet 2 or 4 June 1969 M, HUBER ET AL 3,451,279

PAWL AND RATCHET STEPPING MECHANISMS 1 Filed July 10, 1967 Sheet 3 of 4 By N025 27' 4/0754 ATTORN Y) June 24, 1969 M. HUBER ET AL 3,451,279

PAWL AND RATCHET. STEPPING MECHANISMS Filed July 10. 1967 Sheet of 4 FIG 3 United States Patent ABSTRACT OF THE DISCLOSURE The invention discloses a pawl and ratchet mechanism, especially for stepping a number wheel of a counting device. A ratchet wheel of the mechanism is in engagement with an electromagnetically operable pawl for stepping the ratchet wheel round and with a second pawl for preventing back movement. Rigidly rotatable with the ratchet wheel is a toothed wheel which is engaged by a projection for preventing the toothed wheel and therewith the ratchet wheel from overshooting its position on performing a stepping movement, the toothed wheel meshing with a gear wheel of a number wheel of the counting device for indicating a number counted, and with a further gear wheel of a type wheel for printing the number counted. A printed circuit cooperating with a wiper rotatable with the toothed wheel and thus with the number wheel and type wheel, and reciprocatable switching means are provided for automatically resetting the counting device.

Background of the invention The present invention relates to pawl and ratchet stepping mechanism, especially for counting devices.

Pawl and ratchet stepping mechanisms for counting devices are known as such.

Summary of invention It is anobject of the invention to provide a pawl and ratchet stepping mechanism which is simple in construction and reliablein use. More specifically, the mechanism .of the inventionprovides means for preventing overshooting on stepping the mechanism, provides particularly simple-means for rectilinearly guiding an armature of a stepping electromagnet and setting the spring pressure for returning the armature toitsinitial position whenithe electromagnet is deenergized. t

It is a further object of the invention to provide an electric circuit for the electromagnet for automatically resetting the mechanism after having been'operated to an initial position, for example for zeroisinga counting device in connection with which the mechanism is used.

Brief description of the drawings To make theinvention clearly understood, reference will now be made to the accompanying drawings, which being on a smaller scale than that of the preceding figures;

FIG. 3 is a section on the line III--III of FIG. 1;

FIG. 4 is a section on the line IV-IV of FIG. 1; and FIG. 5 illustrates an electric circuit diagram for operating the stepping mechanism and counting device of FIGS. 1 to 4.

Description 07" the preferred embodiment The stepping mechanism shown has a pawl 1 engaging a ratchet wheel 2 under the action of a leaf spring 3. The pawl 1 is pivotally secured by a pivot pin 5 between branches 61 and 62 of an arm 6 (see FIG. 4) which is pivotable about a fixed pin 7 secured to a housing 9. The arm 6 is also pivotally secured by a pivot pin 30 to an arm 10 which is urged towards the ratchet wheel 2 by a spring 11 extending through the arm 10 and bearing at opposite ends against a pair of abutment cams 13,'the arm 10 being longitudinally movable away from the ratchet wheel 2 against the action of spring 11 by means of an electromagnet 4 having an armature 40 rigid with the arm 10.

The spring 11 is of circular cross-section and the ends thereof fit movably into grooves 12 in the abutment cams 13 owing to the grooves 12 being wider than the ends of the spring 11 (see FIGS. 3 and 4). Owing to such loose fitting, movement of the ends of the spring 11 relative to the respective earns 13 is facilitated. The abutment cams 13 are rotatably mounted on the casing 9 for varying the pressure exerted on the arm 10 by the spring 11.

The ratchet wheel 2 is provided on a toothed wheel 14, and the pivotable arm 6 is formed with a retainer in the form of a projection 15 which, when the pawl 1 is in the engaged position shown, engages one of the teeth of the toothed wheel 14. A second pawl 16 pivoted to the housing 9 by a pin 8 engages the ratchet wheel 2 under the action of a spring 39 for preventing reverse rotation of the ratchet wheel 2.

The toothed Wheel 14 also meshes with another toothed wheel 17 secured to a number wheel 18 formed on its periphery with numbers which can be viewed through an opening 19 in the housing 9.

The toothed wheel 14 also meshes with another toothed wheel 20 which is secured to a printing wheel 31 which projects through a cut-out 29 in the housing 9 to enable a number to which the counting device is set to be printed in known manner by means of an impression element (not shown).

The pin 5 protrudes from the arm 6 into a slot 21 in a bent contact spring 22 (see also FIG. 4) which is provided at opposite ends with contact elements 23 and 24. A pin 26 formed on the arm 6 also projects through the slot 21, the length of the slot 21 being such that the contact spring 22 can be slid longitudinally by a limited distance d relative to the pins 5 and 26. The contact elements 23 and 24 are urged by the bent contact spring 22 into contact with two stationary contact elements 231'and 241 (see FIG. 5), which form part of a printed circuit on a cover 30 (FIGS. 2 and 4) secured to the housing 9.

Secured to the ratchet wheel 2 and rotatable therewith is a wiper 27 (see FIGS. 1 and 5) having contact elements 32 and 33. The contact element 32 of the wiper 27 cooperates with stationary contact elements of a printed circuit generally indicated by reference numeral 34, the contact elements corresponding to the digits 1 to 9 of the number wheel being connected to one another and to a conductor 35 of the printed circuit, whereas the stationary contact element corresponding to the digit 0 is not connected to the other stationary contact elements and'to the conductor 35. The stationary contact element 241 is connectable through a conductor 36 and a switch 28 to a terminal 37. The contact element 33 of the wiper 27 cooperates with a bus bar 38 connected through a conductor 41 to a second terminal 42 to which terminal also the coils of two series-connected coils electromagnet 4 are connected. The other end of said coils is connected through a conductor 43 to a third terminal 44.

The mechanism described operates as follows:

For use, an electric direct current source is connected between the terminals 37 and 44 (FIG. 5), the switch 28 it in its open position shown, and electric pulses to be counted are fed to the terminals 42 and 44 from an external source of electric pulses connected between the terminals 42 and 44. Each pulse reaches the coils of the electromagnet 4 through the conductors 41 and 43 and energizes the electromagnet 4 which attracts its armature 40 and moves therewith the arm against the action of the spring 11 (see also FIG. 1). Thus, during a counting operation, the arm 10 is moved to the right, as viewed in FIG. 1, each time the electromagnet 4 is energized by a pulse from the external source. This movement of the arm 10 causes the pawl 1 to disengage from one of the tooth gaps of the ratchet wheel 2 and to engage the succeeding gap under the action of the spring 3, and also causes the projection 15 to disengage the toothed wheel 14. However, the pawl 16 still engages the ratchet wheel 14 and sufiiciently prevents unintentional rotation of the ratchet wheel 2 and the toothed wheel 14. When the electromagnet 4 is deenergized, the arm 10 returns to the position shown in FIG. 1 under the action of the spring 11, the return movement of the arm 10 now causing the pawl 1 to rotate the ratchet wheel 2 through one step. During the rotation of the ratchet wheel 2, the projection 15 enters one of the tooth gaps of the toothed wheel 14 and thus prevents the toothed wheel 14 and the ratchet wheel 2 from rotating too far, that is to say, through more than one tooth spacing. Since the spring 11 exerts a continuous bias the projection 15 is forced against the toothed wheel 14 owing to the arm 6 being forced in the direction towards the toothed wheel 14.

If after the completion of a counting operation it is desired to reset the stepping mechanism so that the number wheel 18 and the printing wheel 31 are in positions respectively to indicate and print the digit 0, the switch 28 is closed. Thereby, the electromagnet 4 is energized by a current flowing from the terminal 37 through the switch 28, conductor 36, contact elements 241, 24, 23, 231, conductor 35, one of the stationary contact elements of the printed circuit 34 (in the position shown in FIG. 5 said one stationary contact element corresponds to the digit 8), contact element 32, wiper 27, contact element 33, bus bar 38, conductor 41, the coils of electromagnet 4, conductor 43, and terminal 44. Thereby, the electromagnet 4, is energized, and as described above the arm 6 is moved towards the right. The pins 5 and 6 move with the arm and slide in the slot 21 of the contact spring 22 until the pin 22, after having travelled through the distance d abuts against the adjacent end of the slot 21 and carries the contact spring 22 with it until it reaches the position shown in FIG. 5 in broken lines. When the contact element 24 of the contact spring 22 disengages the stationary contact element 241 the electromagnet is deenergized so that the arm 6 moves under the action of the spring 11 in the opposite direction whereby the mechanism is stepped forward by one step so that the contact element 32 now v makes contact with the next stationary contact element,

which in the example of FIG. 5 corresponds to the digit 9, When the arm 6 moves in said opposite direction, the contact spring 22 at first remains stationary until the pin 5 on the arm 6 after having travelled through the distance d abuts against the adjacent end of the slot 21. Thereupon the pin 5 carries the contact spring 22 with it to assume its position shown in full lines in FIG. 5, in which position the contact element 24 again makes contact with the contact element 241. This causes he m gn t 4 to be energized .4 again in the manner described above, and so on. Thus, the wiper 27, the ratchet wheel 2, the toothed wheel 14, the number Wheel 18 and the printing wheel 31 are stepped around until the contact elements 32 and 33 engage contact elements (corresponding to the digit 0) which are not connected to the bus bar 38 and to other contact elements. In this position of the Wiper 27 the electric circuit for energizing the electromagnet 4 remains interrupted so that the mechanism comes to rest. The switch 28 is now opened and the mechanism is ready for a next counting operation.

Thus, during a resetting operation of the stepping mechanism, the contact spring 22 and the contact elements 23 and 24 thereon are reciprocated by the arm 6 and thus intermittently interrupt and bridge the fixed contact elements 231 and 241 to deenergize and energize the electromagnet 4. By means of the limited movement of the contact spring 22 relative to the pins 5 and 26, it is ensured that during each operation of the stepping mechanism the electromagnet 4 is not deenergized by interruption of the current path between the fixed contacts 231 and 241 until the ratchet wheel 2 has been moved by the pawl 1 through an arc corresponding to one tooth of the ratchet wheel 2. The resetting is terminated by the wiper 27 in cooperation with the printed circuit 34 including the bus bar 38 when the number wheel 18 has been rotated to bring the zero on the number wheel 18 adjacent to the opening 19 in the housing 9. j

The arrangement may be employed for high speed oper ation and may be made with small physical dimensions.

It should be clearly understood that the embodiment described and illustrated is given by Way of example, and that modifications, omissions and additions are possible without departing from the spirit of the invention.

We claim: r

1. In a pawl and ratchet stepping mechanism comprising a ratchet wheel, a toothed wheel mountedfor rotation with said ratchet wheel, a pawl movable relative to said ratchet wheel for stepping said ratchet wheel, and a retaining member mounted for movement on movement of said pawl, the features that said retaining member is arranged to engage the toothing of said toothed wheel and to move out of engagement with said toothing dur ing at least part of each stepping movement of said pawl, said retaining member being shaped and arranged to extend between adjacent teeth of said toothed wheel during each stepping movement prior to the stepping movement of said pawl being completed and a movable memher, said pawl being pivotally secured to saidmovable member for eflfecting the stepping movement of said pawl, said retaining member being carried by said movable member to move therewith.

2. A mechanism as defined in claim 1, and further comprising a spring said movable member being biased by said'spring in the direction towards said ratchet wheel, said spring being a smoothly curved leaf spring of subtantially circular cross-section. Y i

3. A mechanism as defined in claim 2, and further comprising an abutment cam, said spring engaging 'a groove in said abutmentcam, said abutment cam being eccentrically mounted for adjusting the bias of said spring by turning said abutment cam.

4. A mechanism as defined in claim 3, wherein said groove is wider than said spring so that said spring fits movably into saidgroove to facilitate movement of said spring within said groove. t

' I 5. In a pawl and ratchet stepping mechanism comprising a ratchet wheel, a toothed wheel mounted for rotation with said ratchet wheel, a pawl movable relative to said ratchet wheel for stepping said ratchet wheel, and a retaining member mounted for movement on movement of said pawl the combination comprising fixed electric contact elements, a slidable contact member cooperating with said fixed contact elements for closing and opening an electric circuit, means for reciprocating said slidable contact member thereby to control said electric circuit, said reciprocating means being mounted for movement in dependence on the movement of said pawl, said slidable contact member having a slot into which project said reciprocating means, said retaining member being arranged to engage the toothing of said toothed wheel and to move out of engagement with said toothing during at least part of each stepping movement of said pawl, a movable member, said pawl being pivotally secured to said movable member for effecting the stepping movement of said pawl, said retaining member being formed as a projection in one piece with said movable member, and a spring, said movable member being biased by said spring in the direction towards said ratchet wheel.

References Cited UNITED STATES PATENTS 1,565,336 12/1925 Seufert 74-128 1,924,776 8/1933 Flanders et all. 200-156 US. Cl. X.R. 

